Method of producing toluene



Allg. 1.3, 1945." v N F |NN l 2,405,660

METHOD OF PRODUCING'l TOLUENE Filed Oct. 17, 1942 2 Sheets-Sheet lmxocsn 5 7; 88 5o 5 mw .if

N. F. LINN @940,650

' METHOD oF PRoDUcING TOLUENE l Filed oct. 17,1942 2 sheets-sheet 2Patented Aug. 13, 1946 METHOD OF PRODUCING TOLUENE Norman F. Linn,Mountainside, N. J., assignor to Standard Oil Development Company, acorporation of Delaware Application October 17, 1942, Serial No. 462,323

3 Claims.

The-present invention is directed toward the production of automotivefuel and, more particularly, it relates to a method of improving ahydrocarbon oil boiling in the naphtha and/or gas oil range,particularly as regards octane number, which naphtha or gas oi1 is ofthe Fischer type. By Fischer type naphtha or gas oil, I refer tohydrocarbons synthesized from CO and Hz in the presence of a knownsuitable catalyst and under known conditions of temperature, pressure,etc.`

As is generally known, hydrocarbons may be Fischer synthesized in thepresence of suitable catalysts such as iron, nickel or cobalt eitheralone or deposited on a carrier such as kieselguhr or kaolin. This maybe promoted and stabilized by alkalies and manganese and copper. Theseproducts, however, have a very low octane number since they are largelycomposed of normal parafns. Broadly speaking, my invention comprisesimproving the octane rating of such a hydrocarbon oil by subjecting itto a combined hydroforming, solvent extracting and catalytic crackingoperation. It is also concerned with the production of substantiallypure aromatics, e. g. toluene of so-calledl nitration grade. bysubjecting selected fractions to a combination of processes which willbe more Vcompletely described below. By hydroforming I mean to imply anoperation in which the treated oil is subjected to elevatedtemperatures, say of the order of 9001000 F. and pressures of 10D-400lbs. per square inch and in the presence of a catalyst, chromia ormolybdena alone or supported on activated alumina, orother VI groupoxide or a mixture of suldes, such as nickel and tungsten suldes, andalso employed in the presence of added hydrogen. The hydroformingoperation is, for the most part, one of dehydrogenation With theformation of aromatics and olens from paraiiins, accompanied also bysome cyclization of paraiiins, aromatization, isomerization and crackingof parafns, but the operation generally is conducted under conditionssuch that there is a minimum changein the boiling range of the chargingoil.

In the accompanying drawings, vIl have indicated diagrammatically a flowplan illustrating a preferred modification of my invention.

Referring tothe drawings fora better understanding of my invention, aFischer synthetic Ahydrocarbon is introduced'into the present Systemthrough line l and thence distilled in a fractionator 3 into anvoverhead fraction boil-k fraction is withdrawn through line 5, condensedin a cooler I and thence discharged through line 8 into a naphthastorage Vessel l0.

The bottoms from distillation zone 3 and boiling say from 440-650o F.are Withdrawn through line I5, condensed in a cooler Il, thencedischarged through line I9 into a gas oil storage vessel 20.

The overhead fraction and the gas oil bottoms from the distillation zone3 are treated as will be lmore fully explained hereinafter. At theoutset it is explained that the naphtha is subjected to reforming in thepresence of hydrogen, While the gas oil is cracked. The reformingoperation results in the production of aromatics which may be solventlextracted to recover, for example, toluene with a degree of puritysuitable for nitration.. The gas oil cracking also results in theproduction of an automotive fuel of high octane number, together withtoluene of a high degree of purity.

Continuing the description of the process shown in the drawings, thenaphtha in storage vessel I0 is 'Withdrawn through a line 35 and thencedischarged into a heater 32, which may be a furnace or other suitableheating means, Where it is heated to reaction conditions, thence ldischarged through line 35 into a reactor 45 containing a catalyst ofthetype previously indicated. Hydrogen from 50 is Withdrawn through line52, heated in a red coil or other heating means `53, and thencedischarged through line into reactor 40 so it is present with the oilundergoing treatment. vWith respect to operating conditions, thefollowing give good results:

Hydrogen proportion is in the range of from say 2000-4000 cubic feet perbarrel of cold oil. Under these conditions the naphtha undergoesreforming, and the reformed products are withdrawn through line anddischarged through Within the range of fromvlZS-fize 1F., which .5 5 acooler 62. and thence discharged'through line 13G-210 F. andrepresenting about 44 volume' per cent of the oil in line 853 iswithdrawn f through line 38 and discharged after cooling into condenser90 and thencefintoa gasoline storage vessel |80. The bottomsfraction'representing about 39 volume per cent of the product fed to thefractionator 55 is Withdrawn'through line 55, condensed in a cooler 97and thence discharged into line 88 where it mixes with the lighter endsfrom the iractionator and ow's with the latter into gasoline storagevessel |00. Thus from the reforming omration, the lighter and heavierends are recovered as gasoline blending agents.

Referring again to fractionator 85, a side cut representing about 17% ofmaterialcharged to `85 and boiling within the range of from about21d-259 F. is withdrawn as a side stream through line 55; This fractionis purified by solvent treatment, preferably, although other means maybe employed. Thus, for example, thissfraction contains normally not onlythe toluene, but also parailins boiling within the range of 21e-250 F.and a minor amount of oleiins also boiling within this range, althoughthe' presence of hydrogenf tends to saturate olens formed in reactor Ml,so that the final result of the reforming operation is to producejparafns andaromatics. As

i indicated, these paraiiins in the vboiling range of from 210-250 F.may be removed',y for instance,

by cracking them to products -whichwill boil lower` than the toluene sothat aftercracking, the toluene maybeseparated kby simple distillation.In the drawings, however, I have shown solvent treating employing SO2 asthe selectiveV solvent forthe aromatics. Toward this end, the

` SO2 is withdrawn from lthe source illand dischargedl intothe top ofsolvent extraction Vessel |5 Where it flows-countercurrently to thehydrocarbon oil fraction entering from 55. f Asa further aid to theprocess, a paraftlnicwash solvent such aspentane isV withdrawnffrom thestorage vessel |25- andv discharged-through line z$22 into solventextraction tower H5 ofcourse, in sol- "Vent extraction tower ||5 theusual formation of raffinate and extract phases takes place. 4Theraffinate phase is withdrawn through line and discharged into astripping tower |35. This rainate is stripped to remove the SO2 which iswithdrawn through line |45 and pumped by pump |1i2 to storage vessellill. The bottoms from stripper are withdrawn through line |45 anddischarged into fractionating column |41. The overhead fractioncomprising the paraiiinic wash vsolvent is Withdrawn from thefractionator |47 through line |49, condensed in condenser |55, vthencepumped backv through line |5| to the parafn storage .|2ll.. The bottomsfrom fractionator |41 are Withdrawn through line |55 and 'dischargedinto line |51 leading to gasoline stor` age vessel |55. The bottomsWithdrawn `from Yfractionator Ml through line |55 maybe dischargedthrough line |55 to either the reforming lzone 4i) or the 'cracking zone320. -I As previouslyindicated, there is"an"'e'Xtract 4 phase formed inextraction vessel ||5 and this is Withdrawn through line |69 anddischarged into stripper |52 where the solvent is removed bydistillation, withdrawn through line |63 and pumped by pump |54 intostorage vessel I Hl. The substantially solvent-free extract is Withdrawnfrom stripper |62 through line |15 and discharged into.y a fractionatingcolumn |15.- The parafns still remaining or associated with the toluenecut are withdrawn through line |85, condensed in a condenser |32 andthence discharged through line |83 into paraninc wash solvent storage|20. The toluene is recovered from fractionator |75 through line andthence discharged into an acid treating vessel |92 where it is treatedpreferably with sulfuric acid of polymerizing strength, such as about65% by Weight, or it may be treated with` a polymerizing clay topolymerize the olei'lns to convert them to heavier polymers which may beseparated from the toluene by distillation. The thus treated material isWithdrawn through line |95 and discharged into fractionator 28|] fromwhich lighter ends may be withdrawn through line 2id, While the heavierpolymers are withdrawn through line 2 2. The desired toluene iswithdrawn as a side stream through line 265 and delivered into a toluenestorage vessel 258. The toluene in 268 has a degree of puritysuii'icient for making trnitrotoluene or any other product requiring ahigh degree of purity. A

Referring to the heavy bottoms of the original Fischer product, it willbe recalled that these were collected in storage drum 25. This materialis to be subjected to-catalytic cracking and towards this end it iswithdrawn through vline 350, discharged into a suitable fired coil orother heating means 3|0 where it is heated to cracking temperatures, sayfrom S25-925 F. and thence withdrawn through line 3|2 and dischargedinto a catalytic cracking reactor 325 where it contacts a crackingcatalyst such as an acid treated montmorillonite clay or a syntheticcracking catalyst consisting vof silica :and alumina or silica andmagnesia. The catalysts,- as Well as cracking conditions for thisoperation are known to the art. Normally good results are obtained byoperating ata temperature of 875 F; andat a relatively low pressure andpermitting Ycontactbetween the catalyst and oil vapors at-reactiontemperatures of from 15-25 seconds or more. Under these A- conditionsthe gas oil undergoes cracking to form catalytically cracked gasoline ingood yields thereof amounting to 35-4070. The cracked products arewithdrawn through line 335 and discharged into fractionating column 335.Unconverted gas is withdrawn from fractionator 335 through line 34B andthence discharged into storage Vessel 20 for further treatment. However,a portion vof this oil is Awithdrawn continuously through liney342,Yparticularly as it becomesincreasingly refractory, and the thusWithdrawn oil may be usedfor a heating oil or for some other purpose.The normally gaseous constituents are Withdrawn i overhead fromfractionator 335 through line 358.

f 4`These gases contain butylene, isobutylene, normal butano andisobutane and they maybe processed `in means not illustrated to form byalkylation branchV k'chainV hydrocarbons boiling Within the gasolinerange, or they may be'converted to syn- 'thetic rubber intermediatessuchY as butadiene, or otherwise-rdisposedof.v q

A 'fraction boiling within the rangeolB` from "e-40|lfF. is withdrawnfrom fractionator 335 `throughiine-360 and discharged intoa'fractonating 'column 310. AThe product entering 310 is dividedpreferably into three fractions as follows: first, an overhead fractioncontaining the lighter ends which is withdrawn through line 380 andcondensed in a cooler 38| and thence discharged into stream 88 where itflows with the overhead from the reforming operation into gasolinestorage vessel I. The bottoms from fractionator 310 may be withdrawn.through line 390, condensed in cooler 39| and also discharged intogasoline storage vessel |00. Finally, an intermediate cut boiling from21o-250 F. and representing about 10% of the material discharged intofractionator 310 is Withdrawn as a side stream through line 400, andthis may be discharged into line 99 to recover with the product from thereforming operation, its toluene content, in a manner which has alreadybeen described.

In an alternate modification, the intermediate cut boiling from 210-250F. which is withdrawn from fractionator 310y through line 400 Vmay-bedischarged into line |58 for ultimate reforming in zone G or passedthrough lines |56 and 305 to coil 3| and thereafter cracked.

Many modifications of the invention as above set forth may be madewithout departing from the spirit thereof. I have shown solventextracting a toluene fraction with liquid sulfur dioxide. Instead ofusing this method, I may use another solvent such as phenol, in whichoperation the vapors to be extracted are treated with liquefiedanhydrous phenol. This process or the process of extracting the liquidSO2 do not form per se the gist of my invention and any known method forrecovering toluene by solvent extraction may be employed. If the solventis SO2 the temperature maintained in the extraction zone I I5 should befrom O to -60 F. or lower. The flow of SO2 with respect to thehydrocarbon should be from 1-3 parts by Weight of SO2 per weight ofhydrocarbons and the volume of paraffinic wash solvent, for example,pentane from |20 should be from 1/2 to 11/2 volumes of the wash solventper volume of liquid consisting of SO2 and the hydrocarbon in theextractor ||5.v Of course, it will be appreciated that in reactors 40and 320 the reactions therein taking place result in the deposition ofcokey or tarry deposits on the catalyst and these operations must beinterrupted intermittently to remove these deposits since theydeactivate the catalyst. This can be accomplished in known manner byburning off the tarry or cokey deposits with an oxygen-containing gas.

In the foregoing disclosure, I have described my process in terms offixed or stationary beds of catalyst. My process may be carried outusing a suitable powdered catalyst suspended in the reaction vapors inthe several reaction Zones. Thus, the reforming and/or crackingoperations may be carried out by flowing the vapors to be cracked orreformed through a zone where they contact a uidized powdered catalystwhich is suspended in said vapors.

Also, of course, in the operationsl described there will come a timewhen it is necessary to regenerate the catalyst in the reactionk zones.This may be accomplished, after discontinuing the flow of oil to thereaction Zones, by treating .the catalyst with an oxygen-containing gas,such as air, or air diluted with fiue gas, at temperatures elevatedsufficiently to cause burning o-f the fouling deposits. This procedureis well known in the art. Where the catalyst in powdered form moves inand out of the reactors, it may be regenerated in separate regenerationzones and thus render the operation continuous.

Another ramification of my process as herein described involves-including the reproportionating of xylenes, formed during thereforming, with benzene in the presence of a suitable catalyst such asAlCla whereby additional quantities of toluene may be produced. Thedetails of this process are generally known in the prior art.

What I claim is:

l. A method of producing toluene of high purity from a hydrocarbonproduct obtained by the hydrogenation of carbon monoxide which comprisesfractionating the said hydrocarbon product into a naphtha fraction and agas oil fraction, submitting the latter to a cracking treatment at atemperature of the order o f S25-925 F. in the presence of a catalystsuitable for promoting the cracking of aliphatic hydrocarbons,recovering a fraction boiling at about 210 to about 250 F. from theproduct of said cracking treatment, combining such fraction With thenaphtha fraction obtained in the fractionation of the product of thehydrogenation of carbon monoxide, subjecting the combined `fractions toa reforming treatment at a temperature of the order of S50-1000 F. andunder a pressure of the order of 1GO-400 lbs/sq. in. in the presence ofhydrogen and a catalyst comprising an oxide of a group VI metal,recovering from the product of said treatment a fraction boiling atabout 210 to about 250 F. and treating such fraction to selectivelyseparate therefrom its aromatic content.

2. A process according to claim 1 in which the aromatic content of thefraction produced in the reforming treatment is separated therefrom byextraction with a solvent, followed by treatment of the extract phasewith a parainic hydrocarbon solvent lighter than the parafnichydrocarbon remaining in said extract phase to displace the latter, anddistillation to remove the said lighter parafnic hydrocarbon solventfrom the aromatic hydrocarbon product.

3. A'process according to claim 1 in which the aromatic content of thefraction produced in the reforming treatment is separated therefrom byextraction with a solvent, followed by treatment of the extract phasewith pentane to displace the parafiinic hydrocarbon remaining in saidextract phase, and distillation to remove the pentane from the aromatichydrocarbon product.

NORMAN F. LINN.

